Observation of 4H–SiC to 3C–SiC polytypic transformation during oxidation

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Abstract
We have observed the formation of single and multiple stacking faults that sometimes give rise to 3C–SiC bands in a highly doped n-type 4H–SiC epilayer following dry thermal oxidation. Transmission electron microscopy following oxidation revealed single stacking faults and bands of 3C–SiC in a 4H–SiC matrix within the 4H–SiC epilayer. These bands, parallel to the (0001) basal plane, were not detected in unoxidized control samples. In addition to the 3.22 eV peak of 4H–SiC, Cathodoluminescence spectroscopy at 300 K after oxidation revealed a spectral peak at 2.5 eV photon energy that was not present in the sample prior to oxidation. The polytypic transformation is tentatively attributed to the motion of Shockley partial dislocations on parallel (0001) slip planes. The generation and motion of these partials may have been induced by stresses caused either by the heavy doping of the epilayer or nucleation from defect.